[otrs] cron pop3

Hi, I am a both a linux and OTRS newbie so bear with me please. I have installed OTRS on Ubuntu and have begun configuring things. I have entered pop3 accounts for each queue for users to submit tickets too, only problem is I cannot figure out how to get OTRS to check the pop3 accounts automatically. From the postmaster mail account portion of the admin area I can click run now on each and the emails appear in the proper queue so I know they are configured correctly. I have read I need to set up a cron job to do this automatically but am lost. Any help or guidance on what to edit in the cron file would be greatly appreciated, thanks. Matt